In systems, such as for lubrication which in their operation utilize hydraulic fluid as well as air pressure, undesirable variations in air pressure are disruptive of proper functioning. The detection and control of disruptive air pressure or air flow rate has been difficult of attainment.
By way of example lubrication systems where it is necessary at more or at less regular intervals to apply air pressure impulsed lubricant, especially lubricant in the form of an air spray, must avoid any prolonged malfunction which will starve the associated mechanism of relatively moving parts such as journals, bearings, gear boxes, and the like, in order to avoid overheating and breakdown.
Numerous and varied detection ad signalling devices have been employed with more or less success, but there has been need for a compact, simple, reliable device for monitoring air pressure or air flow rate deviations from a predetermined or preset level, and especially in connection with lubrication systems, and which device will be readily adaptable to convenient location in the system, even though the system may have fault or malfunction signalling means elsewhere therein.